Patent Application
20160084154
1. Field of the Disclosure
This disclosure relates to control components for turbochargers with Variable Turbine Geometry (VTG). More particularly, this disclosure relates to integrated vane-open stops that control the full open position of the VTG mechanism to regulate exhaust gas flow to the turbine.
2. Description of Related Art
Advantages of turbocharging include increased power output, lower fuel consumption and reduced pollutant emissions. The turbocharging of engines is no longer primarily seen from a high power performance perspective, but is rather viewed as a means of reducing fuel consumption and environmental pollution on account of lower carbon dioxide (CO2) emissions. Currently, a primary reason for turbocharging is using exhaust gas energy to reduce fuel consumption and emissions. In turbocharged engines, combustion air is pre-compressed before being supplied to the engine. The engine aspirates the same volume of air-fuel mixture as a naturally aspirated engine, but due to the higher pressure, thus higher density, more air and fuel mass is supplied into a combustion chamber. Consequently, more fuel can be burned, so that the engine's power output increases relative to the speed and swept volume.
In exhaust gas turbocharging, some of the exhaust gas energy, which would normally be wasted, is used to drive a turbine. The turbine includes a turbine wheel that is mounted on a shaft and is rotatably driven by exhaust gas flow. The turbocharger returns some of this normally wasted exhaust gas energy back into the engine, contributing to the engine's efficiency and saving fuel. A compressor, which is driven by the turbine, draws in filtered ambient air, compresses it, and then supplies it to the engine. The compressor includes a compressor wheel/impeller that is mounted on the same shaft so that rotation of the turbine wheel causes rotation of the compressor wheel/impeller.
This disclosure focuses on a Variable Turbine Geometry (VTG) aspect of turbochargers. VTG turbochargers (1) utilize adjustable guide vanes (8) that are pivotally connected to a lower ring (12) and an upper vane ring (16), including various possible rings, and/or nozzle wall. These guide vanes (8) are adjusted to control exhaust gas backpressure and turbocharger speed by modulating the exhaust gas flow to the turbine wheel (5). The guide vanes (8) are pivoted by vane levers (11), which can be located above the upper vane ring (16). Performance and flow to the turbine are influenced by changes of the flow angle to the turbine wheel (5) by pivoting the guide vanes (8).
One goal of VTG turbochargers (1) is to expand the usable flow rate range in practical applications while maintaining a high level of efficiency. To accomplish this, the turbine output is regulated by changing an inflow angle and inflow speed of the exhaust gas flow at a turbine wheel inlet. With VTG turbochargers, this is achieved using guide vanes (8) in front of the turbine wheel (5) that change their angle of attack with exhaust gas flow speed. This reduces lag at slow speeds while opening to prevent exhaust gas backpressure at higher speeds.
With VTG, turbocharger ratios can be altered as conditions change. When the guide vanes (8) are in a closed position, the high circumferential components of the flow speed and a steep enthalpy gradient lead to a high turbine output and therefore to a high charging pressure. When the guide vanes (8) are in a fully open position, the turbine reaches its maximum flow rate and the velocity vector of the flow has a large centripetal component. The advantage of this type of output control over bypass control is that the entire exhaust gas flow is always directed through the turbine and can be converted to output. Adjustments of the guide vanes (8) can be controlled by various pneumatic or electrical regulators.
An exemplary exhaust-gas turbocharger (1) shown in prior art FIGS. 1-3 from U.S. Pat. No. 7,886,536 includes a turbine housing (2) and a bearing housing (3), with a rotating shaft (4). On one end the shaft (4) carries the compressor wheel/impeller (33) and on the shaft's other end the turbine wheel (5). Within the turbine housing (2) on the side of the turbine wheel (5) a volute (6) is formed which in radial direction evolves into a throat (7). Inside the throat (7) adjustable guide vanes (8) are located.
The guide vanes (8) are pivoted from a vane bearing ring (12) and from a thrust- and bearing ring (28) which is by a spacer (29) kept at a certain distance from the vane bearing ring (12), and they are adjustable through an actuator (32) that actuates the unison ring (9). A rotary motion of the unison ring (9) with respect to the vane bearing ring (12) is transmitted onto the guide vanes (8), which can be adjusted within a pre-determined range between the open position and the closed position.
Typically, the closed position of the guide vanes (8) is used to establish (learn) the position of the vanes (8) in relation to the actuator (32). Current vane learn methodology is to “learn” against the vane closed position. While the closed position of the guide vanes (8) is relatively fixed, the actuator position that relates to the closed position of the guides vanes (8) varies due to extensive stackup of clearances and component tolerances between the guide vanes (8) and other components, such as the actuator (32). Due to fixed limited travel of the actuator (32), the open vane position will vary dependent on the learned vane closed position. The learned vane closed position results in the open vane position of the guide vanes (8) in turbochargers varying from one turbocharger to another.
U.S. Pat. No. 7,886,536 discloses an “Exhaust-gas Turbocharger, Regulating Device for an Exhaust-gas Turbocharger and Vane Lever for a Regulating Device”. Vane levers (11) with axial bosses (14) have circularly curved contour segments (22) that provide for rolling movement with the inner circumference of the unison ring (9). This allows the vane lever (11) to roll against the unison ring (9), but does not stop against the unison ring (9) at a full open position.
U.S. Pat. No. 8,328,520 discloses a VTG turbocharger with separately formed vane lever stops. The stop (25) is embodied as a separate component that can be fixed in the guide grate (18) for adjusting the minimum throughflow.
In certain applications, regulating the full open position can be key. Certain turbochargers require full flow capacity of the VTG that may have insufficient maximum flow capacity when the vanes do not fully open. It is desirable therefore to provide a method where the full vane open position is established by a fixed stop.
The disclosure provides a means for controlling the full open position of the VTG mechanism by providing an integrated fixed stop. A vane-open stop for VTG turbocharger mechanisms can be integrated into control components, such as the vane lever, where the stop regulates exhaust gas to the turbine at maximum flow at the full vane-open position. Vane-open stops for the VTG mechanism will: 1) reduce the variation in the vane full open angle, 2) reduce the variation in the overall vane travel span, and 3) prevent contact between the vanes and turbine wheel, thereby minimizing clearance stackup and regulating throughflow in the vane-open positions. The integrated vane-open stop for a VTG turbocharger can take several forms.
The first embodiment modifies the vane lever with a coplanar protrusion to allow adjacent vane levers to stop against one another and possibly integrated bolts in the full open position. This should provide good control of the open position with minimized stackup.
A further embodiment provides integrated bolt locations with features that limit the travel of adjacent vane levers. The vane-stop collars at each bolt location can control adjacent vane levers, such as three vane levers interacting with three adjacent bolts.
Another embodiment modifies the vane lever with a transverse protrusion to allow the vane lever to contact the upper vane ring, including a unison ring. This should provide good control of the open position with minimized stackup.
Each design for vane-open stops is integrated and controls the full open position of the VTG mechanism to regulate maximum exhaust gas flow to the turbine via the adjustable guide vanes. With the “learn” against the vane open position as a new strategy, the actuator learn software will be modified to ensure consistent learn against the new vane-open stop. Also, bias linkage design can be altered so that open stop can be reached under all conditions, but an adjustment to the linkage up or down (more open or closed) is not the primary means to achieve full flow capacity when using integrated fixed vane-open stops.
Advantages of the present disclosure will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:
A turbocharger 1 with Variable Turbine Geometry (VTG) mechanism 30, or variable-geometry turbocharger, is generally known wherein a compressor wheel/impeller 33 is rotatably driven via a shaft 4 by a turbine wheel 5 in a turbine housing 2, including guide vanes 8 that change their angle of attack in front of the turbine wheel 5. A VTG turbocharger 1 may have a vane ring assembly 17 including a lower vane ring 12 (such as a vane bearing ring), an upper vane ring 16 (which may include a unison ring (9)), a series of guide vanes 8 pivotally mounted at least partially between the lower vane ring 12 and upper vane ring 16, and a plurality of spacers 29 positioned between the lower vane ring 12 and upper vane ring 16.
The vane lever 11 further has a pivot means 40 (shown as a dashed circle in
The vane lever 11 may have a protrusion 50 and a base extension 52. The protrusion 50 extends from an arm member 42, and the base extension 52 extends from the base 54 on an opposite side of the pivot means 40 from the protrusion 50. The protrusion 50 and the base extension 52 are preferably coplanar with the base 54. The protrusion 50 on the arm member 42 of one vane lever 11 is designed to contact the base extension 52 of an adjacent vane lever 11 to provide a “stop” at the full open position of the guide vanes 8. This should provide good control of the open position with minimized stackup.
As shown in
As shown, these vane levers 11 also include two arm members 42 and 44 that extend from an opposite end of the vane lever 11 from the base 54 with the aperture 36 for the vane shaft 38 connected to the guide vane 8. The arm members 42 and 44 make the vane lever 11 wider for contacting the bolt 56 while providing a connector slot 46 formed between the arm members 42 and 44 that functionally operate with a control means 48. This embodiment shows axial bosses 14 similar to U.S. Pat. No. 7,886,536 that provide for rolling movement with the inner circumference of the ring 9, but adds the stop function at the vane open position. The vane levers 11 may have various protrusions in differing arrangements.
The vane lever 11 further has a pivot means 40 upon which the vane lever 11 pivots to move the guide vane 8 from closed to open positions. As shown in
The vane lever 11 may have a transverse protrusion 50 on one arm member 42. The transverse protrusion 50 extends substantially perpendicularly upward from an arm member 42. The transverse protrusion 50 is preferably on the same side of the pivot means 40 as the tip of the corresponding guide vane 8. The transverse protrusion 50 on the arm member 42 of each vane lever 11 is designed to contact the upper vane ring 16 to provide a “stop” at the full open position of the guide vanes 8. The vane lever 11 cannot pivot further after the transverse protrusion 50 contacts the upper vane ring 16 as a stop. In
The vane levers 11 are modified with preferred integral and integrated protrusions 50 that function as vane-open stops when contacting other components to control the full open position of the guide vanes 8 of the VTG mechanism 30 to regulate exhaust gas flow to the turbine wheel 5. The integrated protrusions 50 functioning as stops can be incorporated into existing vane lever designs to control the full open position. While certain vane levers 11 would be modified, other components may require only minimal changes.
With the “learn” against the vane-open position as a new strategy different from the vane-closed position, the actuator learn software is modified to ensure consistent learn against the new vane-open stop. The software can control movement of the actuator 32 and thus the vane levers 11 considering the vane-open stop providing maximum exhaust gas flow. With the vane-open strategy, the bias linkage design can also be altered so that open stop can be reached under all conditions. These features with vane levers 11 as vane-open stops should provide good control of the vane-open position.
The invention has been described in an illustrative manner, and it is to be understood that the terminology used is intended to be in the nature of words of description rather than limitation. Many modifications and variations of the present invention are possible in light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims, the invention may be practiced other than as specifically enumerated within the description.
This application claims priority to and all benefits of U.S. Provisional Application No. 61/786,724, filed on Mar. 15, 2013, and entitled “Integrated Vane Stops For Variable-Geometry Turbocharger Mechanism”.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2014/024351 | 3/12/2014 | WO | 00 |
| Number | Date | Country | |
|---|---|---|---|
| 61786724 | Mar 2013 | US |
